Multiple phase claw pole type motor

ABSTRACT

A claw pole type motor includes first and second claw poles opposed to each other and each including a radial yoke portion having an inner diameter side and an outer diameter side, a plurality of pole portions arranged on the inner diameter side, and axially extended, and an outer peripheral side yoke portion extending on the outer diameter side. A stator core is provided having an inner diameter side, and is formed so as to cause the pole portions of the first claw pole to be meshed with the pole portions of the second claw pole. A rotor is arranged on the inner diameter side of the stator core with a circumferential gap being defined therebetween. In order to provide high efficiency while simplifying manufacturing, the first and second claw poles are formed by compacting of magnetic powder.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.11/376,091, filed Mar. 16, 2006 now U.S. Pat. No. 7,714,475, and whichsaid application claims priority from Japanese patent applications JP2005-079282, filed Mar. 18, 2005 and JP 2006-066882, filed Mar. 13,2006, the entire contents of which are hereby incorporated by reference.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to a multiple phase claw pole type motorused in the fields of industry, home electric appliances, motorvehicles, and the like, and, more particularly, to a multiple phase clawpole type motor having an improved stator iron core.

(2) Description of Related Art

Claw pole type iron cores are attracting attention which are provided inordinary rotating electric motors for the purpose of improving the rateof use of magnetic fluxes by increasing a winding factor of windings, asdisclosed in JP-A-2003-333777 for example.

In the conventional rotating electric motor having a claw pole type ironcore, claw poles of the iron core are formed by laminating a rolledplate and, therefore, can only be obtained in a simple shape. Therefore,the conventional rotating electric motor cannot be obtained as adesirable high-efficiency motor.

BRIEF SUMMARY OF THE INVENTION

An object of the present invention is to provide a multiple phase clawpole type motor with high efficiency having claw poles easilymanufacturable.

To achieve the above object, in a multiple phase claw pole type motorhaving a plurality of claw poles including a claw portion extending inan axial direction and having a magnetic pole surface facing a rotor ina state of being separated from the rotor by a small gap, a radial yokeportion extending radially outwardly and perpendicularly from this clawportion, and an outer peripheral yoke extending from this radial yokeportion in the same direction as the direction of extension of the clawportion, a stator core formed by alternately placing the claw poles in acircumferential direction so that a distal end of each claw portionfaces the radial yoke of an adjacent one of the claw poles and having astator constructed by sandwiching an annular coil with the adjacent clawpoles of this stator iron core, the present invention makes the clawpoles formed with a magnetic compact having a DC magnetizing property ofits flux density becoming 1.7 teslas when 10000 A/m of magnetic field isapplied.

The claw pole is formed by compacting a magnetic powder as describedabove. The claw pole can therefore be formed so as to have a complicatedshape. Also, a high-efficiency motor can be obtained by using a magneticcompact having a DC B-H curve of its flux density becoming 1.7 teslaswhen 10000 A/m of magnetic field is applied.

According to the present invention, as described above, a multiple phaseclaw pole type high-efficiency motor having claw poles easilymanufacturable can be obtained.

Other objects, features, and advantages of the present invention willbecome clear from the following description of embodiments of thepresent invention relating to accompanying drawings.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 is an exploded perspective view of a first claw pole and a secondclaw pole used in a first embodiment of a three-phase claw pole typemotor according to the present invention;

FIG. 2 is a perspective view partly in section of a part of stator ironcores for three phases obtained by assembling the first and second clawpoles shown in FIG. 1;

FIG. 3 is a schematic longitudinal sectional view of the entirethree-phase claw pole type motor according to the present invention;

FIG. 4A is a sectional view taken along line A-A in FIG. 3;

FIG. 4B is a sectional view taken along line B-B in FIG. 3;

FIG. 4C is a sectional view taken along line C-C in FIG. 3;

FIG. 4D shows the construction of an inductor type rotor;

FIG. 4E shows the construction of a rotor having an inductor andmagnets;

FIG. 4F shows the construction of a salient pole type rotor;

FIG. 5A is a diagram showing B-H curves of various iron core materials;

FIG. 5B is a diagram showing B-H curves of various iron core materials;

FIG. 6A is a diagram showing a mesh model of the iron core and theresults of computation on the various iron core materials usingthree-dimensional magnetic field analysis;

FIG. 6B is a diagram showing the results of calculation of output torqueof the motor constructed of various iron core materials;

FIG. 6C is a diagram showing the relationship between the flux densityand the output torque of the motor, constructed of various iron corematerials, at 10000 A/m;

FIG. 6D is a diagram showing the relationship between the claw polethickness and the output torque of the motor constructed of an SMC (SoftMagnetic Composite);

FIG. 6E is a diagram showing the relationship between the flux densityand the output torque of the motor, constructed of various iron corematerials, at 10000 A/m;

FIG. 7A is a sectional view showing a main flux and a leakage flux inthe claw pole;

FIG. 7B is developed plan view showing a leakage flux in the claw pole;

FIG. 8 is a diagram showing the results of computation of therelationship between the shape of the claw portion of the claw pole andthe effective value of the linkage flux using three-dimensional magneticfield analysis;

FIG. 9 is a perspective view partly in section of a second embodiment ofthe three-phase claw pole type motor according to the present invention;

FIG. 10 is a sectional view partly in section of a third embodiment ofthe three-phase claw pole type motor according to the present invention;

FIG. 11 is a perspective view partly in section of a fourth embodimentof the three-phase claw pole type motor according to the presentinvention;

FIG. 12 is a sectional view partly in section showing the relationshipbetween the magnetic poles and the claw poles shown in FIG. 11;

FIG. 13 is an exploded plan view showing an example of modification ofthe fourth embodiment;

FIG. 14 is an enlarged view partly in section of a fifth embodiment ofthe three-phase claw pole type motor according to the present invention;

FIG. 15 is a partly exploded perspective view of a sixth embodiment ofthe three-phase claw pole type motor according to the present invention;

FIG. 16 is a partly exploded perspective view showing an example ofmodification of the sixth embodiment;

FIG. 17 is a perspective view of a claw iron core of a seventhembodiment of the three-phase claw pole type motor according to thepresent invention;

FIG. 18 is a perspective view of a claw iron core of an eighthembodiment of the multiple phase claw pole type motor according to thepresent invention;

FIG. 19 is a perspective view showing an example of modification of clawpoles;

FIG. 20 is a perspective view showing another example of modification ofclaw poles;

FIG. 21 is a perspective view showing still another example ofmodification of claw poles;

FIG. 22A is a diagram showing the results of measurement of the inducedelectromotive force of the claw pole type motor using iron plates suchas SPCC;

FIG. 22B is a diagram showing an induced voltage waveform at therotating speed of 250 r/min; and

FIG. 22C is a diagram showing an induced voltage waveform at therotating speed of 1000 r/min.

DETAILED DESCRIPTION OF THE INVENTION

Hereafter, a first embodiment of a multiple phase claw pole type motoraccording to the present invention will be described on the basis ofFIGS. 1 to 4.

A three-phase claw pole type motor is constructed by a rotor 2constructed on a rotating shaft 1, a stator 5 formed concentrically withthis rotor 2 in a state of being separated from the same by a small gapformed in a circumferential direction, and a stator frame 7 on which thestator 5 is supported. The rotating shaft 1 is rotatably supported onopposite ends of the stator frame 7 by bearings 8A and 8B.

The rotor 2 is constructed by a rotor iron core 3 formed concentricallywith the rotating shaft 1, and a plurality of magnetic poles 4 formed ofpermanent magnets fixed on the outer periphery of the rotor iron core 3.The stator 5 is constructed by stator iron cores 6U, 6V, and 6W, andannular coils 13 wound on the stator iron cores 6U, 6V, and 6W. Thestator iron cores 6U, 6V, and 6W are supported on the stator frame 7,and the rotating shaft 1 is rotatably supported by the bearings 8A and8B on the opposite ends of the stator frame 7.

Each of the stator iron cores 6U, 6V, and 6W is constructed by a firstclaw pole 9A and a second claw pole 9B. Each of the first claw pole 9Aand the second claw pole 9B is constructed by a claw portion 10 having amagnetic pole surface 10F extending in an axial direction and facing therotor 2 while being seperated from the same by the small gap, a radialyoke portion 11 extending radially outwardly and perpendicularly fromthe claw portion 10, and an outer peripheral yoke 12 extending from theradial yoke portion 11 in the same direction as the direction ofextension of the claw portion 10. Each of the radial yoke portion 11 andthe outer peripheral yoke 12 has a circumferential length L2 twice orlonger than the circumferential length L1 of the claw portion 10. Theclaw portion 10 is connected to one side along the circumferentialdirection of the radial yoke portion 11 having the circumferentiallength L2. The outer peripheral yoke 12 has an axial length L4 of about½ of an axial length L3 of the claw portion 10.

The first claw pole 9A and the second claw pole 9B are formed intoshapes identical to each other by compacting a magnetic powder in a die.In this way, a complicated magnetic pole structure can be obtained incomparison with those constructed by laminating silicon steel plates.

The first claw poles 9A and the second claw poles 9B formed as describedabove are alternately arranged in the circumferential direction so thatthe end of the claw portion 10 faces the inside diameter side of theradial yoke portion 11 of the adjacent claw pole 9A or 9B, thus formingthe stator iron core 6U incorporating the annular coil 13U. The statoriron cores 6V and 6W incorporating the annular coils 13V and 13W areformed in this way and placed by the side of the stator iron core 6U inthe axial direction with shifts of 120° in terms of an electrical angle,as shown in FIGS. 4A to 4C, thus constructing the three-phase claw poletype motor having the same number of magnetic poles 4 as the number ofclaw portions 10, i.e., sixteen magnetic poles 4. These three groups ofstator iron cores 6U, 6V, and 6W are encapsulated in a molded insulatingresin to obtain the stator 5 in which the first claw poles 9A, thesecond claw poles 9B, and the annular coils 13U, 13V, and 13W arecombined integrally with each other.

The construction of the rotor 2 is not limited to the construction ofarranging the magnets 4 on its surface, but it is possible to obtainrunning torque so long as the rotor 2 is a rotor, which constructs apole, such as a rotor which has saliency as shown in FIG. 4F, a cagetype inductor shown in FIG. 4D, and a rotor which has magnets and aninductor as shown in FIG. 4E.

As described above, a complicated magnetic pole construction, in otherwords, a magnetic pole construction capable of improving the motorefficiency can be obtained by forming the first claw poles 9A and thesecond claw poles 9B by compacting a magnetic powder.

FIGS. 5A and 5B show the results of measuring the B-H curves of each rawmaterial. This measurement was performed by a ring sample type measuringmethod (JIS H 7153), and shows DC B-H curves. Iron core bodies formed bycompacting a magnetic powder (soft magnetic composites i.e. SMCs 1, 2,and 3) ordinarily have a magnetic permeability lower than that oflaminated iron cores formed of a rolled plate (SPCC t0.5, SS400) andlaminated iron cores formed of a silicon steel plate (50A1300, 50A800).The maximum flux density of the former is also lower than that of thelatter. Further, even if they have the completely same shape, the ironcores (SMCs) formed by compacting a magnetic powder differ in B-H curvesby compounding ratios of an iron powder and a resin binder, and thelike. As shown in FIG. 5B, the flux density of the SMC 1 obtained when amagnetic field of 10000 A/m is applied to its compact is 1.7 teslas ormore, and when 80000 A/m, which is large magnetic field strength isapplied, the flux density exceeds 2 teslas. On the other hand, the fluxdensity of the SMC 2 obtained when the magnetic field of 10000 A/m isapplied to its compact is 1.6 teslas, and when 80000 A/m, which is largemagnetic field strength is applied, the flux density is 1.8 teslas orso. As for an SMC 3, its flux density obtained when the magnetic fieldof 10000 A/m is applied to its compact is only 1.26 teslas, and when80000 A/m, which is large magnetic field strength is applied, the fluxdensity is less than 1.5 teslas. It can be expected that the obtainedtorque of the SMC 3 where the flux density as an SMC is low is alsosmall when it is used in a motor.

FIGS. 6B to 6E show the results of calculation of the output torque ofmotors in three-dimensional magnetic field analysis using a finiteelement method. First, a mesh model is shown in FIG. 6A. In thisexample, one cycle of electrical angle (equivalent to a machine angle of45°) of a three-phase claw pole motor with outside diameter size of φ60mm and 8 poles is modeled. FIG. 6B shows the result of calculation ofthe output torque, obtained when a current is given to a coil of eachphase using this model, using the B-H curves of each material. In theconsequence of calculation on the condition that shapes of the motorswere completely the same, it was found that, as for the output torque ofthe motors, the higher a magnetic permeability of a material was, thehigher the output torque was. That is, according to the results ofcalculation with four kinds of materials shown in FIG. 5B, the torque ofSPCC is the largest, and the torque of the SMC 3 is the smallest. FIG.6C shows this relationship with taking the flux density at the time of10000 A/m as a horizontal axis and taking the output torque as avertical axis. It was found that the output torque became large inproportion to the flux density.

Next, since the SMC can obtain its core shape by compacting, it ispossible to employ a pole shape which improves efficiency, as describedpreviously. A specific method is to change pole thickness, which was alimit for SPCC, or the like. FIG. 6D shows the results of calculationwith having increased the thickness of the SMC and having performed thesame calculation as the above. It becomes clear that, when the thicknessof claws of the SMC increases under the same conditions of the fieldmagnets and the motor size, the output torque had an optimal value. FIG.6E shows the result of plotting with superposing this optimal value onFIG. 6C having been explained previously. It was confirmed that the SMC1 exceeded the limit torque in the case of construction from SPCC.

Hence, in this embodiment, it is easy to manufacture the claw poles 9Aand 9B and is possible to obtain a multiple phase claw pole type motorhighly efficient than a conventional iron plate bending type claw polemotor by not only performing the compacting a magnetic powder to formthe claw poles 9A and 9B, but also constructing a claw pole stator coreof the SMC compact which has DC magnetizing properties of 1.7 teslas ormore when a magnetic field of 10000 A/m is applied to the SMC compact.

In addition, since the multiple phase claw pole motor constructed of theSMC core is hardly influenced by an eddy current loss, it is alsoadvantageous to be able to be driven at an RF (radio-frequency).Although the comparison of the output torque in FIG. 5 mentioned abovewas at low speed (a frequency area with slight influence of an eddycurrent), properties of the motor constructed of the SMC core willfurther improve in an RF. FIG. 22A shows the relationship between therevolution speed and the effective value of no-load inducedelectromotive force. In a claw pole motor constructed from iron platessuch as SPCC, when the revolution speed becomes large, an eddy currentflows inside the iron plates in a direction of obstructing magneticfluxes. Then, owing to a denial operation of the magnetic fluxes by thecurrent, a waveform of the induced electromotive force is distorted asshown in FIG. 22B, and an effective value becomes small. On the otherhand, in the claw pole motor whose core is constructed of the SMC, sincean eddy current hardly flows, it becomes an effective value of theinduced electromotive force linear to a frequency (revolution speed).Hence, although the conventional claw pole type motor with theconventional claw poles could not be used for an application at highrevolution speed, the claw pole motor constructed of the SMC core can bedriven at high revolution speed (high frequency area).

In addition, because the eddy current hardly flows it is also possibleto correspond to a pulse width modulation (PWM) method of control systemwhich performs a pulse division of a sinusoidal voltage and driving. PWMis a drive system of obtaining an effective value of a voltage in apulse-like voltage. Since a switching frequency of those pulses isusually about 10 times of a maximum frequency of a drive current of amotor, that is, a very high frequency, an eddy current arises by its RFcomponent. Hence, since iron loss becomes large in a conventional clawpole motor constructed from iron plates, the motor has become aninefficient motor. Since the eddy current hardly flows, the claw poletype motor of the present invention which is constructed of the SMC corecan be driven.

On the other hand, large torque pulsation occurs in the case of use ofthe iron core formed by compacting a magnetic powder, such that themagnitude of pulsation is ⅓ of the average torque. The cause of thistorque pulsation is a large distortion in the waveforms of voltagesinduced in the annular coils 13U to 13W by local magnetic saturation inthe claw poles 9A and 9B. Such a waveform distortion is also caused byan interpole leakage flux or an in-pole leakage flux.

These leakage magnetic fluxes will be described with reference to FIGS.7A and 7B. FIG. 7A shows a flow of a main flux Φ. The main flux Φemerging from one N magnetic pole in the magnetic poles 4, for example,enters the claw portion 10 of the first claw pole 9A through a gap,enters the claw portion 10 of the second claw pole 9B from the clawportion 10 of the first claw pole 9A in linkage to the annular coil 13,and enters the S magnetic pole 4 from the claw portion 10 of the secondclaw pole 9B through the gap, thus forming a magnetic path returning tothe N magnetic pole 4. Apart from the main flux Φ, an interpole leakageflux Φ1 exists. If the interpole size SO between the claw portions 10 ofthe first and second claw poles 9A and 9B is smaller than the gap sizebetween the magnetic poles 4 and the claw portions 10, the interpoleleakage flux Φ1 forms a magnetic path by shortcutting between the clawportions 10 without linkage to the annular coil 13, resulting inreduction in a rate of use of the magnetomotive force of the magneticpoles 4 formed of permanent magnets. The interpole size SO between theclaw portions 10 may be increased by considering this phenomenon.However, if the interpole size SO is increased, the width of themagnetic pole surface 10F is so small that the effective value of thelinkage flux of linkage between the main flux Φ and the annular coil 13is considerably reduced. It is not advisable to adopt such an easy wayof increasing the interpole size SO.

Further, the generation of an in-pole leakage flux Φ2 is a phenomenon inwhich, as shown in FIG. 7B, part of the main flux Φ entering the clawportion 10 of the first claw pole 9A enters the radial yoke portion 11of the adjacent second claw pole 9B facing the first claw pole 9A fromthe distal end of the first claw pole 9A by forming the in-pole leakageflux Φ2, and flows in the radial yoke portion 11 in the circumferentialdirection to form a magnetic path reaching the claw portion 10 of thesecond claw pole 9B. To reduce this in-pole leakage flux Φ2, a sectionalarea of the distal end of the claw portion 10 may be reduced byincreasing the angle θk of the magnetic pole surface 10F or the gap dlbetween the distal end of the claw portion 10 and the radial yokeportion 11 may be increased. These measures to reduce the in-poleleakage flux Φ2 entails the drawback of reducing the area of themagnetic pole surface 10F and thereby reducing the effective value ofthe linkage flux as in the above-described case. It is not advisable toadopt these measures.

FIG. 8 shows the results of computation of the relationship between theinterpole size SO and the effective value of the linkage flux using theabove-mentioned three-dimensional magnetic field analysis.

As is apparent from FIG. 8, the effective value of the linkage flux canbe increased by increasing the angle θk of the magnetic pole surface 10Fand by reducing the interpole size SO of the adjacent claw portions 10.However, if the effective value of the linkage flux is increased, theleakage fluxes (Φ1, Φ2) are also increased to cause an increase indistortion of the waveform of the induced voltage, as described above.

A second embodiment of the three-phase claw pole type motor inaccordance with the present invention arranged to solve theabove-described problem due to the leakage fluxes (Φ1, Φ2) and capableof maintaining a high effective value of the linkage flux will bedescribed with reference to FIG. 9. In FIG. 9, the same referencecharacters as those in the figure showing the first embodiment indicatethe same component parts. The description of the same component partswill not be repeated.

In this embodiment, the angle θk of the magnetic pole surface 10F isincreased and the thickness T of the claw portion 10 is increased. Also,the thickness T is gradually increased along a direction from the distalend of the claw portion 10 toward the radial yoke portion 11.

If the sectional area of the claw portion 10 is increased as describedabove, a high effective value of the linkage flux can be maintained.Also, local magnetic saturation regions in the first and second clawpoles 9A and 9B can be reduced. As a result, the leakage fluxes (Φ1, Φ2)are limited even if the interpole size SO is reduced by increasing theangle θk of the magnetic pole surface 10F. Therefore, distortion in thewaveform of the induced voltage can be reduced and torque pulsation canbe limited.

FIG. 10 shows a third embodiment of the three-phase claw pole type motorin accordance with the present invention. The third embodiment differsfrom the first embodiment in the sectional shape of the magnetic pole 4in the rotor side.

That is, in this embodiment, the magnetic pole 4 is formed so as to havea sectional shape with a convex curve such that a central portion in thecircumferential direction is closest to the claw portion 10 whileopposite end portions in the circumferential direction are remotest fromthe claw portion 10.

If a curved surface defined by such a convex curve is formed on themagnetic pole 4, the main flux Φ can be made to flow concentrically froma center of the curved surface into the claw portion 10. Also, theresistance of the magnetic flux path for the interpole leakage flux Φ1flowing in the claw portions 10 through the opposite end portions of themagnetic pole 4 in the circumferential direction as shown in FIG. 7A isincreased by increasing the gap between the magnetic pole 4 and the clawportion 10, thereby reducing the amount of leakage of this flux. As aresult, the interpole leakage flux Φ1 can be reduced without reducingthe effective value of the linkage flux.

A fourth embodiment of the three-phase claw pole type motor inaccordance with the present invention in which the shape of the clawportion 10 is changed to reduce a leakage flux will be described withreference to FIGS. 11 and 12.

The area of the magnetic pole surface 10F of the claw portion 10 facingthe magnetic pole 4 is increased to ensure a high effective value of thelinkage flux. The area of the magnetic pole surface 10F is increased byreducing the angle θk in the construction shown in FIG. 1 so that thesides defining the angle θk are parallel to the axial direction. Also,the interpole size SO between the claw portions 10 of each adjacent pairof the first and second claw poles 9A and 9B is increased relative tothe gap between the claw portions 10 and the magnetic poles 4, but theinterpole size So between portions of the claw portions 10 having athickness t in the magnetic pole 4 side is reduced.

If the claw portions 10 are formed in this manner, the flow of theinterpole leakage flux Φ1 into the portions having the thickness t,between which the magnetic path between the claw portions 10 isrestricted, is limited, thereby reducing the interpole leakage flux Φ1.

To reduce the in-pole leakage flux Φ2, the gap d2 between the distal endof the claw portion 10 and the radial yoke portion 11 of the adjacentclaw pole 9A (or 9B) may be increased.

A leakage flux Φ3 between adjacent pair of phases can be reduced, forexample, by setting the gap d3 between the distal end of the clawportion 10 in the U-phase side and the radial yoke portion 11 of theadjacent claw pole 9A in the V-phase side to an increased value, asshown in FIG. 13.

FIG. 14 shows a fifth embodiment of the three-phase claw pole type motorin accordance with the present invention.

In this embodiment, to enable the main flux Φ to flow through theshortest distance, concave portions R1 and R2 formed of polygonalsurfaces are respectively formed as an inner corner portion in theconnecting portion between the claw pole 9A or 9B and the radial yokeportion 11 and an inner corner portion in the connecting portion betweenthe radial yoke portion 11 and the outer peripheral yoke 12. The concaveportions R1 and R2 are formed by connecting a certain number of surfacesat certain angles. They may alternatively be formed of one curvedsurface or a certain number of curved surfaces.

A sixth embodiment of the three-phase claw pole type motor in accordancewith the present invention will be described with reference to FIG. 15.The same basic construction for increasing the effective value of thelinkage flux between the first claw pole 9A and the second claw pole 9Band reducing leakage fluxes as that in each of the above-describedembodiments is also used in this embodiment. The description of thebasic construction will not be repeated.

A three-dimensional shape can be integrally formed since the first clawpole 9A and the second claw pole 9B constructing each of stator cores6U, 6V, and 6W are formed by compacting a magnetic powder, as describedabove. Since the first claw pole 9A and the second claw pole 9B areformed so as to be identical in shape to each other, it is desirable toattach marks used as a reference at the time of assembly to the firstand second claw poles 9A and 9B. Further, it is advantageous to providea positioning function or an assembly guide function by forming themarks. Such a function is effective in improving the facility with whichthe component parts are assembled and reducing the assembly time.

To provide such a function in this embodiment, recesses 14 andprojections 15 capable of engaging with the recesses 14 are formed inthe outer peripheral yoke 12 constructing the first claw pole 9A and thesecond claw pole 9B. The recesses 14 and the projections 15 are formedin the first and second claw poles 9A and 9B by being recessed andraised along the axial direction so as to be capable of fitting to eachother when the first and second claw poles 9A and 9B are brought intoabutment on each other. A recessed groove 14 and a projection 15 areformed at positions distanced by 180° in terms of electrical angle inthe circumferential direction. Since the first and second claw poles 9Aand 9B are perfectly identical in shape to each other, they can becompacted in one die.

When the first and second claw poles 9A and 9B constructed as describedabove are assembled, they are fitted to each other by simply moving theprojections 15 into the recesses 14 in the axial direction, with theannular coil 13 interposed between the claw portions 10 and the radialyoke portions 11. Thus, the assembly can be easily completed.

FIG. 16 shows an example of modification of the sixth embodiment. A leadwire channel 16 through which a lead wire 13R corresponding to awinding-leading end and/or a wiring-trailing end of the annular coils 13is laid to the outside is formed by integral compacting in each of thesurfaces of the radial yoke portions 11 of the first and second clawpoles 9A and 9B facing the annular coil 13.

If the lead wire channel 16 is formed in the radial yoke portion 11 inadvance, the need for provision of an additional space for the lead wire13R is eliminated, thereby increasing the winding density of the annularcoil 13 and enabling lead wires 13R in the entire motor to be laid in adetermined direction.

While the facility with which the first and second claw poles 9A and 9Bin the in-phase relationship are assembled is improved in theabove-described sixth embodiment, an improvement in the facility withwhich the first and second claw poles 9A and 9B in an interphaserelationship are assembled can be achieved in a seventh embodiment shownin FIG. 17.

That is, a recess 16 and a projection 17 are formed in the radial yokeportion 11 side in the outer peripheral yokes 12 of the first and secondclaw poles 9A and 9B in an interphase relationship by being placed sideby side in the circumferential direction, in addition to the recess 14and the projection 15 shown in FIG. 15. Recesses 16 each capable ofbeing fitted to one projection 17 provided at least in one place areformed at positions distanced by ±60° and ±120° in terms of electricalangle from the position of the projection 17, thereby enabling the outerperipheral yokes 12 of the first and second claw poles 9A and 9B ininterphase relationship to be positioned relative to each other withaccuracy as well as facilitating the assembly.

FIG. 18 shows an eighth embodiment of the multiple phase claw pole typemotor in accordance with the present invention. Fitting holes 18 and afitting projection 19 arranged in the axial direction are formed in theouter peripheral yokes 12 of the first and second claw poles 9A and 9Bin interphase relationship, as are the projection and the recesses inthe sixth embodiment. Also in this case, the same effect as that in thesixth embodiment is achieved.

In each of the above-described embodiments, the first and second clawpoles 9A and 9B are formed in correspondence with each pole. However,needless to say, a claw pole assembly 20 in which claw pole portions forone phase (360°) are formed integrally with each other as shown in FIG.19, a claw pole assembly 21 in which claw pole portions for ½ phase(180°) are formed integrally with each other as shown in FIG. 20 and aclaw pole assembly 22 in which claw pole portions for ¼ phase (90°) areformed integrally with each other as shown in FIG. 21 may be formed. Insuch case, the relationship between the positions at which the recesses14 or 16 and the projections 15 or 17 are provided and the relationshipbetween the positions at which the fitting holes 18 and the fittingprojections 19 are provided may be angular relationships of integermultiples of ±60° and ±120° in terms of electrical angle.

Although the above-mentioned description was made about embodiments, thepresent invention is not limited to them, but it is apparent to thoseskilled in the art that various changes and modifications can be madewithin the scope of the spirit of the present invention, and theattached claims.

1. A claw pole type motor including a stator core having an innerdiameter side and a rotor arranged at the inner diameter side of thestator core with a circumferential gap being defined between the rotorand the stator core, wherein the rotor extends in an axial direction ofthe motor, and the motor is controlled by a pulse width modulationsystem, the motor comprising: first and second claw poles each includinga radial yoke portion having an inner diameter side and an outerdiameter side, a plurality of pole portions connected to the innerdiameter side at connection portions to the radial yoke portion andarranged to extend in the axial direction from the inner diameter sideof the radial yoke portion, and an outer peripheral side yoke portionarranged on the outer diameter side of the radial yoke portion, whereinthe first claw pole and the second claw pole are formed by compressionmolding of magnetic powder, wherein the stator core is formed by thepole portions of the first claw pole and the pole portions of the secondclaw pole being meshed with one another, wherein the first and secondclaw poles are formed to have the same shape as one another, whereineach of the first and second claw poles has a claw portion, a crosssection of which gradually increases in the radial direction and in theperipheral direction toward a root of the claw pole, and wherein aninterpole size between the first claw portion and the second clawportion is larger than a gap between the rotor and the claw portions. 2.A claw pole type motor as set forth in claim 1, wherein the outerperipheral side yoke of the first claw pole has an axial length which isequal to a half of the axial length of the claw portions of both firstand second claw poles.
 3. A claw pole type motor as set forth in claim1, wherein the outer peripheral side yoke of the first claw pole andthat of the second claw pole are opposed to each other so as to defineone outer peripheral surface.
 4. A claw pole type motor as set forth inclaim 1, wherein the first or second claw pole is formed with one phasepart thereof being integrated.
 5. A claw pole type motor according toclaim 1, wherein each of the first claw portion and the second clawportion has a distal end which is reduced by increasing an angle betweenrespective side surfaces of the claw portion in the peripheraldirection.